Non-conventional hexagonal structure for boric acid

When a special preparation procedure has been applied, the crystallization system of boric acid has been changed from triclinic to hexagonal: at temperatures between 60 and 70 °C, under controlled pH conditions, the boric acid belonging to triclinic system was mixed with d-glucose, calcium carbonate, and calcium hydroxide. Thermal analysis evidenced a final compound with quite similar thermal behavior as that of initial triclinic boric acid but having some differences in decomposition kinetics. X-ray diffraction analysis showed a new compound, named HBA, belonging to the hexagonal crystallization system with the following lattice parameters: a = b = 20.4869 Å and c = 12.1506 Å. This strong anisotropic structure was also confirmed by the hexagonal form of the crystallites, grown from HBA and water solutions, which have been observed with a light polarized optical microscope. Exotic polycrystalline conglomerates grown from water solution of HBA have nice colours that are changing when they are set different angles between polarizer and analyser. FTIR measurements revealed the IR absorbance bands belonging to O–H, O–B, and H–O–B bonds of the trigonal planar boric acid, for both crystallographic systems, but some small differences between wave-numbers and peak intensities were encountered. Finally, the dielectric properties of the water solutions of HBA are analyzed by performing electric susceptibility measurements at different temperatures, from 25 to 50 °C.     

In situ molecular spectroscopic evidence for CO2 intercalation into montmorillonite in supercritical carbon dioxide

The interaction of anhydrous supercritical CO(2) (scCO(2)) with both kaolinite and ~1W (i.e., close to but less than one layer of hydration) calcium-saturated montmorillonite was investigated under conditions relevant to geologic carbon sequestration (50 °C and 90 bar). The CO(2) molecular environment was probed in situ using a combination of three novel high-pressure techniques: X-ray diffraction, magic angle spinning nuclear magnetic resonance spectroscopy, and attenuated total reflection infrared spectroscopy. We report the first direct evidence that the expansion of montmorillonite under scCO(2) conditions is due to CO(2) migration into the interlayer. Intercalated CO(2) molecules are rotationally constrained and do not appear to react with waters to form bicarbonate or carbonic acid. In contrast, CO(2) does not intercalate into kaolinite. The findings show that predicting the seal integrity of caprock will have complex dependence on clay mineralogy and hydration state.     

The use of stable isotopes ratios for authentication of fruit juices

The determination of the content of stable isotopes, ¹⁸O and ²H, respectively, in juice water facilitates the distinction between authentic juices and juices made from concentrates by redilution with tap water. At the same time, the detection of C₄ cane or corn-derived sugar syrups in fruit juices which are produced from C₃ fruit types is thus facilitated by the characteristic differences in ¹³C/¹²C, expressed as δ ¹³C (‰) values due to photosynthetic CO₂ assimilation via the C₃₋, C₄₋, and crassulacean acid metabolism pathways. In this study, the quantitative determination of water added to an authentic juice, on the basis of δ ¹⁸O, and δ ²H values, respectively, was successfully performed. Also, the δ ¹⁸O, and δ ²H of juice water and δ ¹³C of the whole juice in 18 samples were also determined. The results obtained provided us with the possibility of distinguishing between authentic fruit juices and those obtained by redilution of concentrated fruit juices and the detection of C⁴ type added sugar.     

Magnetic properties and magnetocaloric effects in ferrimagnetic compounds

Magnetic properties and magnetocaloric effects were studied in (Gd_xY_1?x)₃Co₁₁B₄ ferrimagnetic compounds. Rather high values of the entropy changes were shown in large temperature ranges. The ΔS values were correlated with high temperature dependences of resultant magnetizations determined mainly by the gadolinium sublattice one. Large relative cooling power was also shown.     

A five-dimensional perspective on the Klein–Gordon equation

We discuss the Klein–Gordon (KG) equation using a path-integral approach in 5D space–time. We explicitly show that the KG equation in flat space–time admits a consistent probabilistic interpretation with positively defined probability density. However, the probabilistic interpretation is not covariant. In the non-relativistic limit, the formalism reduces naturally to that of the Schrödinger equation. We further discuss other interpretations of the KG equation (and their non-relativistic limits) resulting from the 5D space–time picture. Finally, we apply our results to the problem of hydrogenic spectra and calculate the canonical sum of the hydrogenic atom.     

SERS assessment of the cancer-specific methylation pattern of genomic DNA: towards the detection of acute myeloid leukemia in patients undergoing hematopoietic stem cell transplantation

In this label-free surface-enhanced Raman scattering (SERS) study of genomic DNA, we demonstrate that the cancer-specific DNA methylation pattern translates into specific spectral differences. Thus, DNA extracted from an acute myeloid leukemia (AML) cell line presented a decreased intensity of the 1005 cm⁻¹ band of 5-methylcytosine compared to normal DNA, in line with the well-described hypomethylation of cancer DNA. The unique methylation pattern of cancer DNA also influences the DNA adsorption geometry, resulting in higher adenine SERS intensities for cancer DNA. The possibility of detecting cancer DNA based on its SERS spectrum was validated on peripheral blood genomic DNA samples from n = 17 AML patients and n = 17 control samples, yielding an overall classification of 82% based on the 1005 cm⁻¹ band of 5-methylcytosine. By demonstrating the potential of SERS in assessing the methylation status in the case of real-life DNA samples, the study paves the way for novel methods of diagnosing cancer.

Graphical abstract

     

Stable reconstruction of the T(2) distribution by low-resolution NMR measurements and the classical markov and hausdorf momentum problem

Assuming that an original distribution is a probabilistic measure and the Laplace transforms are known only for a finite number of points that are affected by errors, we develop a method for reconstructing weak-sense mean values obtained by integrating smooth functions with the measure. Our method is useful in NMR if the NMR signal can be represented as a superposition of exponential terms. In these circumstances, we show how the data processing can be related to the classical Hausdorf momentum problem. First, we clarify the meaning of stable spectrum reconstruction, and then develop stable filtering and a mean value reconstruction algorithm. Our method has been tested on both simulated and real sets of spin–spin relaxation curves with noise. In view of this, our method could provide an efficient and accurate reconstruction of spin–spin relaxation data. For any reader interested in applications, a “practical recipe” that is almost self-consistent has been included.     

Stable isotopes determination in some Romanian fruit juices

The characterisation of 45 Romanian single-strength fruit juices (apples, pears, plums and grapes) collected from different Transylvanian areas by means of stable isotope approach are presented and discussed in this study. We measured (2)H/(1)H, (18)O/(16)O ratios from water juice and (13)C/(12)C from pulp and compared these results with those already reported in the literature for single-strength juices, in order to see how the geographical and climatic conditions of Transylvania and the meteorological peculiarities of the year 2010 influence the isotopic composition of the investigated fruit juices. The δ(13)C mean values that we found for apple pulp picked up from different Transylvanian areas show slight differences, probably due to the environmental conditions of the plants. No significant correlation either between the variety of apple or the geographical origin and δ(13)C value was established.     

Characterization of Phenolics in Lavandula angustifolia

ABSTRACT

The lavender flowers and their essential oil are widely used in therapy in Romania and the European Community. Since the European Pharmacopoeia only allows the use of Lavandula sp flowers for medicinal purposes, the objective of this study was to investigate the chemical composition of Lavandula angustifolia extracts obtained by ultrasound-assisted extraction, rapid pressurized extraction at 6.7?bar, and subcritical fluid extraction. The solvents used for the first two methods were mixtures of water and alcohol, glycerin, and propylene glycol. These extracts were analyzed by high-performance thin-layer chromatography, infrared spectroscopy with attenuated total reflectance, and Raman spectroscopy. The total phenolics were evaluated using a modified Folin–Ciocalteu method. The primary phenolics were chlorogenic acid, gallic acid, umbelliferone, luteolin 7-O-glucoside, vitexin, and isoquercitroside. The extracts were variable in composition, with the highest yield by subcritical fluid extraction, followed by extraction at 6.7?bar. The infrared and Raman spectroscopy results confirmed the chromatography measurements.